Science Enabled by New Measurements of Vegetation

Structure (ICESat-II, DESDynI, etc.)  

Some Ecological Considerations

Jon Ranson & Hank ShugartCo-Chairs

2

Science Question

How are the Earth's carbon cycle and ecosystems changing, and what are the consequences for the Earth's carbon budget, ecosystem sustainability, and biodiversity?*

The CARBON CYCLE: Carbon in the atmosphere is a controlling factor on climate and hence on ecological productivity and the sustainability of life.

*Earth Science Enterprise Strategy, October 2003Science Mission Directorate Draft Science Plan, 2006

3

Science Question

How are the Earth's carbon cycle and ecosystems changing, and what are the consequences for the Earth's carbon budget, ecosystem sustainability, and biodiversity?*

*Earth Science Enterprise Strategy, October 2003Science Mission Directorate Draft Science Plan, 2006

How are the Earth's carbon cycle and ecosystems changing, and what are the consequences for the Earth's carbon budget?*

4

Science Question Components

Carbon in the aboveground

biomass of forests

represents about 85% of

the total carbon in the Earth’s aboveground

biomass.

Olson et al. 1983http://cdiac.ornl.gov/

epubs/ndp/ndp017/ndp017.html

Composited NDVI map from MODIS showing global forest extent

The question requires measurements of three-dimensional vegetation structure to estimate:(1) Carbon in Aboveground Vegetation

(2) Ecosystem Properties

Aspen Allometry Superior National Forest

0

5

10

15

20

25

0 5 10 15 20 25

Diameter Breast Height (cm)

Bio

mas

s (k

g/m

2)

Series1

Aboveground biomass and carbon storage

•Terrestrial vegetation biomass surveys at regional and global scales are fundamental to quantify the strength, location and extent of land carbon sinks and sources. •To estimate biomass regionally and globally we must measure forest structure attributes, harvest the trees, weigh all components and develop allometric relationships. •Currently measurements can only be done in situ over limited areas.

3-D structure of terrestrial vegetation

Critical not only for biomass surveys and biomass change but also for quantifying the location, nature, cause and extent of disturbance in rapidly degrading or recovering terrestrial ecosystems.

Current global measurements of carbon in

vegetation are very laboriously obtained

To Atmosphere

To Land/Ocean

Fossil Fuels Land Use Change

Ocean Uptake

Unidentified(“missing”)Terrestrial

Sink

Peta (1015) grams of carbon/year

Atmospheric Carbon

Veg3D will reduce major uncertainties and help to

explain the “missing carbon sink.”

Largest remaining uncertainties about the Earth’s carbon budget are in its terrestrial components.

4.2 ± 0.2

7.2 ± 0.5

Land Use Change

1.5 ± 1.0

2.2 ± 0.82.3 ± 1.5

Global Carbon Budget (Canadell et al., 2007)

Millennium Ecosystem Assessment Synthesis Report (2005)

Uncertainty in the magnitude of carbon emissions from land use changes is 66%

of the estimated input (1.5

petagrams)

Land Use Change

1.5 ± 1.0To

Atmosphere

Fire

Climate and human-induced ecosystem changes are reflected strongly in the vertical height and density

distribution of vegetation and its horizontal heterogeneity.

Both human-induced and natural disturbance are major driving forces that determine the transition of forest stands,

landscapes, and regions from carbon sink to source and back again.

To Atmosphere

To Land/Ocean

Fossil Fuels Land Use Change

Ocean Uptake

Unidentified(“missing”)Terrestrial

Sink

Peta (1015) grams of carbon/year

Atmospheric Carbon

Vegetation structure will reduce major uncertainties

and help to explain the “missing carbon sink.”

Land Use Change

1.5 ± 1.0

2.3 ± 1.5

Global Carbon Budget (Canadell et al., 2007)

USA ± China

China+China ± USA

The vertical dimension provides key insight into ecosystem state and function based on the heights of canopy and understory

Return Intensity

Vertical Structure

Changes in landscape spatial heterogeneity - vegetation type, height profiles and biomass relate strongly to ecosystem state and condition.

Ecosystem structure may change in response to climate. Top – change in tree form from bush to erect Bottom – Pinus siberica appearing in the understory of a Larix forest in Siberia

In this radar image from Canada there is evidence of fires ( dark areas at top) and logging (e.g.,black features in center)

Horizontal Structure

10

Science Question

How are the Earth's carbon cycle and ecosystems changing, and what are the consequences for the Earth's carbon budget, ecosystem sustainability, and biodiversity?*

*Earth Science Enterprise Strategy, October 2003Science Mission Directorate Draft Science Plan, 2006

How are the Earth's carbon cycle and ecosystems changing, and what are the consequences for the Earth's ecosystem sustainability?*

Ecosystem sustainability

implies a capacity to

measure and predict the state of the

planet’s ecosystems.

Baobab Grove in N’Xia Pan, Botswana

A Primer on the Dynamics of Forest Ecosystems

Tropical Rain Forest Canopy in the Brazilian Amazon

Forest Gap-Dynamics Cycle

Lidar Image of Mature Tropical Rain Forest

In a mature forest, one expects the canopy to be a mosaic of spatial elements about the size of a large tree crown. These elements go through a cyclical recovery cycle.

What do gap dynamics tell usabout forest biomass dynamics?

Expected Biomass Change Recovery from Disturbance

Carbon Sink

Carbon Source

Carbon Sink

time

Mature forest is a mosaic.

Carbon disturbance recovery dynamics are non-linear as the all-aged successional patches become desynchronized to produce the mixed-aged mature-forest mosaic.

Successional patches recovering from disturbance

Depending on antecedent history, a forest with the biomass level associated with a mature forest, could be storing carbon, losing carbon or staying the same.

This means that a single biomass “snapshot” does not completely reveal forest carbon dynamics.

La Selva Footprint Level Height Change (2005-1998)

2005

1998

Amplitude

Ele

vati

on

Footprint centers within 3 m

17

Science Question

How are the Earth's carbon cycle and ecosystems changing, and what are the consequences for the Earth's carbon budget, ecosystem sustainability, and biodiversity?*

*Earth Science Enterprise Strategy, October 2003Science Mission Directorate Draft Science Plan, 2006

How are the Earth's carbon cycle and ecosystems changing, and what are the consequences for the Earth's biodiversity?*

The three-dimensional structure of vegetation provides habitats for many species and is a control on biodiversity.

primary tropical forest

Vegetation height and the vertical distribution of leaves and branches influence where and how other species utilize the ecosystem for food, shelter, and territory.

Flooded Forest

Coastal Redwood Forest

Vietnamese Subtropical Forest

Eucalyptus forest

The horizontal pattern of habitat-use varies by several

orders of magnitude depending on species

This implies a need for wall-to-wall coverage of vegetation structure to capture all of these multiple scales